Semiconductor processing involves a number of different chemical and physical steps whereby minute electronic devices are created on a substrate at the front end of a fabrication process. Integrated circuits are constructed using multilayers of interrelated patterns of various materials, the layers being created by such processes as chemical vapor deposition (CVD), physical vapor deposition (PVD), and epitaxial growth. Some layers are patterned using photoresist masks and followed by wet and dry etching techniques.
Patterns are created within layers by the implantation of dopants at particular locations. The substrate upon which the devices are created may be silicon, gallium arsenide, glass, or other appropriate material.
In the production of integrated circuits upon the substrate, back end of production involves connecting the fabricated semiconductor devices on the chip with electrically conductive materials. This back-end-of-line (BEOL) “wiring,” which is the electrical connection scheme for connecting semiconductor devices, completes the circuits as designed to function within the total integrated circuit device. Metal lines are used in the metallization process as electrical connections between semiconductor devices.
Increased semiconductor device performance can be achieved, at least in part, through the further miniaturization of features such as transistors. Decreased feature sizes and decreased spacings between features allow more features to be placed in a unit area for greater device performance. As feature densities increase, the widths of the conductive lines and the spacings between the conductive lines also need to scale smaller.